Dispersants for a hydraulic composition are chemical admixtures, and used for dispersing cement particles, thereby reducing a unit water quantity necessary for achieving a required slump and enhancing workability and the like of a hydraulic composition. Examples of conventionally-known dispersants include naphthalene-based dispersants such as a formaldehyde naphthalenesulfonate condensate, polycarboxylic acid-based dispersants such as a copolymer of a monomer having a carboxylic acid and a monomer having an alkylene glycol chain, and melamine-based dispersants such as a melaminesulfonic acid-formaldehyde condensate.
Compared to polycarboxylic acid-based dispersants and melamine-based dispersants, naphthalene-based dispersants are characterized in that they have smaller fluctuations in exhibiting the fluidity in response to changes of materials or temperatures, and a hydraulic composition obtained thereby has a relatively low viscosity and they are easy to use in manufacturing a hydraulic composition.
JP-A 61-281054 describes a chemical admixture for concrete, which contains a cement dispersant and a specific nonionic surfactant at a predetermined weight ratio.
JP-A 2003-165755 describes a workability-improving agent for improving workability of a cement composition, which contains a specific polyalkylene oxide derivative and/or a specific hydrocarbon derivative. JP-A 2003-165755 also describes a cement water-reducing agent containing the workability-improving agent and a water-reducing agent.
JP-A 55-023047 describes a slurry, which is composed of water and a hydraulic composition containing a β naphthalenesulfonic acid formaldehyde condensate and a nonionic surfactant having an oxyethylene chain.
JP-A 60-011255 describes a cement additive, which is composed of a formalin condensate of a metal salt of naphthalenesulfonate and a polyoxyethylene-based compound.
JP-A 48-028525 describes a method for manufacturing a concrete product, which includes molding a desired concrete product with concrete additionally containing an anionic surfactant, and performing atmospheric pressure steam curing of the molded product.
Meanwhile, use of a surfactant as a cement chemical admixture has also been conventionally proposed. JP-A 50-150724 describes a cement chemical admixture, which contains an anionic surfactant of sulfuric ester type and a polyoxyalkylene- or polyhydric alcohol-based nonionic surfactant.